fertilidad de suelos y nutricion de plantas en el trópico
TRANSCRIPT
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Soil Fertility and Plant Nutrition
in the Tropics and SubtropicsA. Amberger
About this book and its author
This book is published jointly by the International Potash Institute (IPI) and the
International Fertilizer Industry Association (IFA). It discusses the possibilities
and constraints to food production on the many different soil types found in
tropical and subtropical countries. By indicating ways in which crop nutrition
and hence crop production can be increased on these soils in developing
countries, the author shows ways to ensure food security and improve
livelihoods.
Professor Dr. A. Amberger has had much experience in the tropics and
subtropics, co-ordinating and organizing agricultural research programmes and
serving as a consultant to international organizations. The topics discussed inthis book are a synthesis of Professor Amberger's considerable experience and a
testimonial to his many years of collaborative scientific effort. The text is based
largely on his lectures to students at the Technical University of Munich and at
international congresses.
International Fertilizer Industry Association
International Potash Institute
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Soil Fertility and Plant Nutrition
in the Tropics and SubtropicsA. Amberger
International Fertilizer Industry AssociationInternational Potash Institute
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Soil Fertility and Plant Nutrition in the Tropics and SubtropicsA. Amberger
First version, published by IFA and IPIParis, France; Horgen, Switzerland, 2006
Copyright 2006 IFA. All rights reservedISBN 2-9523139-0-3
International FertilizerIndustry Association28, rue Marbeuf
75008 Paris, FranceTel: +33 1 53 93 05 00Fax: +33 1 53 93 05 45/ [email protected]
Printed in FranceLayout: Claudine Aholou-Pütz, IFAGraphics: Hélène Ginet, IFA
(iii)
Acknowledgments
I wish to thank A. Krauss (lately of IPI), who initially agreed that IPI would
publish this book, and H. Magen (IPI) and P. Heffer (IFA), whose continued
support and helpful comments have brought this work to fruition.
I especially thank M. Trenkel (lately BASF) for much valuable discussion and
his support and encouragement that have enabled me to complete the writing
of this book. I also thank the many colleagues and regional collaborators for
their scientific help over many years.
A.E. Johnston (Rothamsted Research) gave helpful comments and suggestions
for some additional material. My thanks to him for this and also for editing themanuscript on behalf of IPI and IFA.
I gratefully acknowledge permission to use the following photographs: Plate 1,
V. Romheld; Plate 4, IPI; Plate 6, R. Buresh.
Finally, I wish especially to thank Mrs. I. Neumayr and Mrs. B. Menzel for their
secretarial assistance, and Mrs. C. Aholou-Pütz and Ms H. Ginet (IFA) for the
layout of the manuscript and of the graphics in preparation for printing.
A. Amberger.
Freising/Weihenstephen
January 2006
The designation employed and the presentation of material in thisinformation product do not imply the expression of any opinionwhatsoever on the part of the International Fertilizer Industry
Association or the International Potash Institute. This includesmatters pertaining to the legal status of any country, territory, city orarea or its authorities, or concerning the delimitation of its frontiersor boundaries.
International Potash InstituteP.O. Box 5698810 Horgen, Switzerland
Tel:+ 41 43 8104922Fax: +41 43 [email protected]
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(iv)
Table of Contents
1. Introduction 1
2. Characteristics of the tropics and subtropics 2
2.1. Climate and natural vegetation 2
2.2. Soil formation 3
2.3. Factors related to soil fertility 5
2.4. Constraints to crop production 12
2.5. Nutrient sources 20
2.6. Irrigation 27
2.7. Soil and plant analysis 30
3. Humid tropics and subtropics 32
3.1. Climate, natural vegetation and cropping potential 32
3.2. Properties of selected soil types 33
3.3. Constraints and recommendations 36
3.4. Land use and farming systems 38
3.5. Summary 41
4. Semi-humid and semi-arid tropics and subtropics - rainfedsavannas 42
4.1. Climate and natural vegetation 42
4.2. Properties of selected soil types 43
4.3. Constraints and recommendations 46
4.4. Land use and farming systems 49
4.5. Summary 53
5. Arid tropics 54
5.1. Climate and natural vegetation 545.2. Properties of selected soil types 55
5.3. Constraints and recommendations 57
5.4. Land use and farming systems 59
5.5. Summary 60
6. Rice cropping and rice soils 61
6.1 Soils and cropping systems 61
6.2. Nutrient management 62
7. Salinity 65
8. Micronutrients 71
8.1. Soils and cropping systems 71
8.2. Micronutrient deficiencies 74
8.3. Managing micronutrients 75
8.4. A case study evaluating micronutrients 76
9. Conclusions and outlook 80
10. General reading and references 82
10.1. General reading 82
10.2. References 82
11. Annex. Plates 89
(v)
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Plates
Plate 1. Rhizosphere pH as affected by plant species 89
Plate 2. Severe water erosion in Sudan 89
Plate 3. Raising water to the surface by a “‘saiga” wheel to
discharge to a canal, Egypt 90
Plate 4. Modern irrigation system in Brazil 90
Plate 5. Drip irrigation system in Egypt 91
Plate 6. Omission plot setup to assess nutrient requirements in
Tamil Nadu, India 91
Plate 7. A typical Ferralsol in southern Brazil 92
Plate 8. An Andosol developed in young volcanic ash in Costa Rica 92
Plate 9. A typical Vertisol in The Philippines 93
Plate 10. Slash and burn of shrub vegetation in West Africa 93
Plate 11. A typical Rendzina in Syria 94
Plate 12. Desert vegetation in Egypt 94
Plate 13. Puddling a rice paddy in India 95
Plate 14. A severely salt-affected soil in Egypt 95
Plate 15. Bare branches and little leaf rosettes due to zinc
deficiency in apples 96
Plate 16. Chlorosis due to iron deficiency in grape vine 96
Acronyms, Symbols and Abbreviations
(as used in this book)
Acronyms
EMBRAPA Empresa Brasileira de Pesquisa Agropecuaria, Brazil
FAO Food and Agricultural Organization of the United Nations
FAOSTAT FAO Statistical Database
ICARDA International Center for Agricultural Research in the Dry Areas
IFA International Fertilizer Industry Association
IFDC International Fertilizer Development Center
IFPRI International Food Policy Research Institute
IPI International Potash Institute
IRRI International Rice Research Institute
ORSTOM Office de la Recherche Scientifique et Technique d'Outre-Mer,
France
PPI/PPIC Potash and Phosphate Institute / Potash and Phosphate
Institute of Canada
SDC Swiss Agency for Development and Cooperation
UNESCO United Nations Educational, Scientific and Cultural
Organization
Symbols
Al Aluminium
B Boron
C Carbon
Ca Calcium
CaCO3 Calcium carbonate
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Abbreviations
AM Arbuscular mycorrhizae
AS Ammonium sulphateASN Ammonium sulphate nitrate
BNF Biological nitrogen fixation
CAN Calcium ammonium nitrate
CAM Crassulacean acid metabolism
CEC Cation exchange capacity
DCD Dicyandiamide
DMPP 3,4-dimethylpyrazole phosphate
dS/m deci Siemens per meter
DTPA Diethylene triamine pentaacetic acid
EC Electrical conductivity
EDTA Ethylene diamine tetraacetic acid
HEDTA N-(2-hydroxyethyl)ethylenediaminetriaceticacid
PR Phosphate rock
mM millimole
MOP Muriate of potash, potassium chloride
NOP Nitrate of potash, potassium nitrate
PPD Phenylphosphodiamidate
SCU Sulphur-coated urea
SOM Soil organic matter
SOP Sulphate of potash, potassium sulphate
SSNM Site-specific nutrient management
SSP Single superphosphate
TSP Triple superphosphate
UAN Urea ammonium nitrate
(viii)
CaSO4 Calcium sulphate
Cu Copper
Fe Iron
H+ Proton
HCO3 Bicarbonate
K Potassium
KCl Potassium chloride (=MOP)
KNO3 Potassium nitrate (=NOP)
K2O Potash
K2SO4 Potassium sulphate (=SOP)
Mg Magnesium
Mn Manganese
Mo Molybdenum
N Nitrogen
NH3 Ammonia
NH4 Ammonium
NO2 Nitrite
NO3 Nitrate
N2 Dinitrogen
N2O Nitrous oxideNaCl Sodium chloride
P Phosphorus
P2O5 Phosphate
S Sulphur
SO4 Sulphate
Zn Zinc
(ix)
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Soil fertility and plant nutrition in the tropics and subtropics 1
1. Introduction
This book considers at both a basic and practical level the constraints to soil
fertility and plant nutrition in the tropics and subtropics. It presents strategiesfor nutrient management for sustainable production that conserve soil
resources. It shows ways to avoid errors in agricultural land use that can lead to
the deterioration of soils and desertification.
It is dedicated to all those interested in sustainable, environmentally
acceptable agriculture including those in research, development and extension
work, consultants, progressive farmers, students and decision-makers. The
contents are based on literature surveys and personal experience gained over
many years especially in Africa, the Near East and Central and South America.
Those who want to work in the tropics and deal with the problems of soil
fertility and plant nutrition there must be able to identify the yield-limiting
factors in each area. This requires knowledge of the climatic and soil
characteristics at their place of work, observation of plant growth and
phenological symptoms, and understanding data provided by soil and plant
analysis. Only then can strategies be developed and recommendations given
that will address local problems.
Meadows et al. (1992) voiced the need for a regenerative agriculture,
which improves the use of soils and utilises natural processes, and similar
needs have been noted in other studies, for example, the IFPRI 2020 Vision
(IFPRI, 2002) and World Agriculture Towards 2015-30 (FAO 2002).
The number of undernourished people in the world declined only
marginally over the past decade, remaining above 800 million (FAO, 2005).
Hunger is prevalent in the tropics and subtropics, areas that are severely affected by soil degradation and loss of soil fertility, and the link between them
is obvious. Soil degradation and loss of fertility leads to poor crop yields which,
in turn, contribute greatly to food insecurity with subsistence farming that is
widespread in the tropics and subtropics.
In summary, the most important goal and challenge in tropical
agriculture must be to sustain and, if possible, increase soil fertility and
maintain food production for millions of people in an economically,
ecologically and socially acceptable way. Knowledge of soil characteristics is abasic requirement for producing location-specific recommendations for
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Soil fertility and plant nutrition in the tropics and subtropics 54
2.3. Factors related to soil fertility
Soil fertility is the result of the interactions between the biological, chemical
and physical properties of soil due to soil type and land use, and the effects of
climate. It is related to the potential for the sustainable production of crops and
animals and can be assessed and/or described in various ways.
2.3.1. Soil colour
Soil colour depends on the type and amount of minerals and organic matter.
Black soils are rich in organic matter and often are very fertile, whereas grey
soils have little organic matter and poor drainage. Brown soils contain an
adequate amount of organic matter, Fe and other minerals, and have gooddrainage. Red soils have large amounts of oxidized Fe and frequently good
drainage but very little organic matter. Yellow soils have both oxidized and
reduced Fe with little organic matter and medium drainage.
2.3.2. Soil physical properties
Soil physical properties include structure, texture, consistency, porosity and
water holding capacity. The structure of a soil is related to the arrangement of
mineral particles into aggregates, which influence the air and water content of the soil, its ability to retain water and its drainage characteristics.
Soil texture is concerned with the size of the mineral particles, which
determines the surface area of the soil. At a simple level, according to particle
size, there is clay (<0.002 mm), silt (0.002-0.05 mm), sand (0.05-2 mm), and
stones (>2 mm). Soils with a large content of clay become hard when dry and
sticky when wet.
Soil consistency is related to the compression/compaction and plasticity of a soil and influences tillage and other mechanical operations. Soil organic
matter has an effect on consistency by helping to bind mineral particles
together. The sensitivity of a soil to erosion is related to texture and
consistency.
Soil porosity refers to the total volume of pores in the soil. Pores can be
filled either with air or water. Large pores allow the rapid exchange of air and
drainage of excess water. Small pores retain water against drainage and the
availability of this water for crops depends on the diameter of the pores. Clay
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Soil fertility and plant nutrition in the tropics and subtropics 9
Base cations such as potassium (K), Ca and magnesium (Mg) become
deficient in the acid soils of the humid tropics. This is due to the small amount
in the parent material, the small CEC to retain them against leaching and their
removal by erosion. Very large losses of K can occur after forest has been cut
and removed (Likens et al., 1994). Losses through soil erosion greatly exceed
those by leaching, highlighting the need to minimize erosion. Burning the
above ground vegetation as a part of shifting cultivation, only leads to a short
transitory increase in the amount of base cations from the ashes. Growing cash
crops, such as vegetables, fruit trees, oil palm, coffee, coconut and tuber plants
that have a large requirement for these nutrients quickly results in deficienciesor imbalances. In cases of severe deficiency, soluble compounds of K, Ca and
Mg can be applied as foliar sprays and crops will show a rapid response.
Potassium has an irreplaceable role in a number of functions in plants but
only small amounts are required relative to the much larger quantities needed
to fulfil its role as an osmotic regulator in all cells (Johnston et al., 2001). Plants
well supplied with K are more resistant to pests and diseases. Furthermore,
beneficial effects of K on the chilling tolerance of plants grown in a warm
climate and to photooxidative stress under high light intensity are well
documented (IPI, 2003, and references therein).
Calcium is important in cell membrane stabilization and enzyme
modulation. Consequently, Ca deficiency exhibits itself as the disintegration
and collapse of cell walls, mainly seen in vegetables and fruit trees, which have
a large Ca requirement.
Magnesium is involved in many metabolic processes. Chlorotic or
necrotic spots spread over the leaves indicate deficiency. Regular applications
of calcitic or dolomitic amendments are required to prevent deficiency.
8
Table 2. Dry weight of wheat roots and shoots and total P in shoots when plants
were grown with (+) and without (-) arbuscular mycorrhizal (AM) fungi (Adapted
from Li et al., 2001)
Treatment Dry weight (g/pot) Total P in shoots (mg/pot)Shoots Roots
– AM 4.0 ± 0.6 0.9 ± 0.4 4.2 ± 1.2
+ AM 7.1 ± 0.1 1.3 ± 0.1 6.1 ± 0.2
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Soil fertility and plant nutrition in the tropics and subtropics 4948
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Fertilizers have to be applied at the correct time using the right
application method. In semi-arid regions, urea and CAN are usually used
having replaced AS, because AS acidifies the soil. The conversion of urea to
NH3, due to urease activity at the high temperature in the tropics and
subtropics, takes place in a few days. The subsequent oxidation to NO3 dependsvery much on soil pH; 1-2 weeks in neutral/alkaline soils and 3-4 weeks in acid
soils.
Sulphur is not a major problem in less intensive traditional cropping
systems but may be with high yielding crops. Sulphur is often deficient in light
textured, highly weathered soils that are poor in organic matter, the only source
of S, because of continuous burning of the vegetation, as well as adsorption of
SO4 on Fe and Al oxides and on any weathered edges of clay particles.
Experiments with oilseeds, oil palm, legumes, vegetables and maize showed
good responses to application of S in West Africa (Table 9). Ammonium
sulphate, SSP, SOP and elemental S added to TSP or to PR can meet the S
requirement of many crops.
4.3.5. Nitrogen and sulphur
Nitrogen deficiency is widespread and a major yield-limiting factor. Symbiotic
and non-symbiotic N fixation, plant residues and animal and human wastes
are the main sources of N for plants in the absence of N fertilizers. The total N
content of the soils in the semi-humid/semi-arid tropics and subtropicsdepends on their content of SOM, the more stable forms of which also play an
important role in retaining water, and the retention of nutrients in plant
available forms. Therefore, increasing the SOM content should be a main
priority. Soils developed from granite or quartzite naturally have a very small
content of SOM. Grassland savanna soils have a high C: N ratio and hardly
release any N for plant uptake. During the dry season, NO3 accumulates in
Alfisols and, at the beginning of the wet season, there is a large flush of mineral
N. However, the largest part of this N will be lost by leaching and througherosion because only a small percentage is used by annual crops.
Table 9. Effect of sulphur fertilization on crop yield in selected countries in West
Africa (Adapted from Kanwar and Mudahar, 1986)
Country Crop % yield increase due to S fertilization
Senegal Groundnuts 6
Burkina Faso Sorghum 14
Cowpea 38
Niger Groundnuts 6
Pearl millet 11
Togo Groundnuts 45
Benin Groundnuts 35
Maize 32
Nigeria Maize 45
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Soil fertility and plant nutrition in the tropics and subtropics 8988
Wissemeier, A.H., Linzmeier, W., Gutser, R., Weigelt, W. and Schmidhalter, U.
(2001) Th it ifi ti i hibit DMPP (E t ®) C i11. Annex. Plates
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(2001). The new nitrification inhibitor DMPP (Entec®) - Comparison
with DCD in model studies and field applications. In: Developments in
Plant and Soil Sciences, Kluwer Academic Publishers, Dordrecht, The
Netherlands.Zehler, E., Kreipe, H. and Gething, P.A. (1981). Potassium Sulphate and
Potassium Chloride: Their Influence on the Yield and Quality of
Cultivated Plants. IPI Research Topics No. 9. International Potash
Institute, Horgen, Switzerland.
Zerulla, W., Pasda, G., Hähndel, R. and Wissemeier, A.H. (2001). The new
nitrification inhibitor DMPP (Entec®) for agricultural and
horticultural crops-an overview. In: Developments in Plant and Soil Sciences. Kluwer Academic Publishers, Dordrecht, The Netherlands.
Plate 1. Rhizosphere pH as affected by plant species
Plate 2. Severe water erosion in Sudan
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Plate 5. Drip irrigation system in Egypt
Plate 6. Omission plot setup to assess nutrient
requirements in Tamil Nadu, India
Plate 3. Raising water to the surface by a “saiga”
wheel to discharge to a canal, Egypt
Plate 4. Modern irrigation system in Brazil
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Plate 9. A typical Vertisol in The Philippines
Plate 10. Slash and burn of shrub vegetation in West
Africa
Plate 7. A typical Ferralsol in southern Brazil
Plate 8. An Andosol developed in young volcanic ash in
Costa Rica
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Plate 13. Puddling a rice paddy in India
Plate 14. A severely salt-affected soil in Egypt
Plate 11. A typical Rendzina in Syria
Plate 12. Desert vegetation in Egypt
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